19 General utilities library [utilities]

19.14 Function objects [function.objects]

19.14.8 Logical operations [logical.operations]

19.14.8.3 Class template logical_­not [logical.operations.not]

template<class T = void> struct logical_not { constexpr bool operator()(const T& x) const; };
constexpr bool operator()(const T& x) const;
Returns: !x.
template<> struct logical_not<void> { template<class T> constexpr auto operator()(T&& t) const -> decltype(!std::forward<T>(t)); using is_transparent = unspecified; };
template<class T> constexpr auto operator()(T&& t) const -> decltype(!std::forward<T>(t));
Returns: !std::forward<T>(t).